Post Myocardial Infarction Papillary Muscle Rupture

Papillary muscle rupture is a mechanical complication of infarction causing acute severe mitral regurgitation.

Occurs 2 to 7 days after infarction in 0.05 to 0.3% of cases.

The posteromedial papillary muscle (single blood supply from the posterior descending artery) ruptures about 6 to 12 times more often than the anterolateral muscle (dual supply).

Often follows a relatively small inferior or posterior infarct.

Rupture may be complete (head or whole muscle, usually fatal in hours) or partial (rupture of a head).

Mortality is about 50% in the first 24 hours with medical therapy alone, and 20 to 40% with surgery.

• Abrupt pulmonary oedema, dyspnoea, hypotension and cardiogenic shock.
• A soft, short systolic murmur may be inaudible because rapid pressure equalisation between the left ventricle and atrium shortens the regurgitant jet.
• Absent thrill, which differentiates from ventricular septal rupture.
• Tachycardia, hypoxaemia, raised lactate.

• Urgent echocardiography (transthoracic then transoesophageal): flail mitral leaflet, ruptured muscle head attached to chordae prolapsing into the left atrium, eccentric severe regurgitant jet, and often hyperdynamic left ventricle.
• Right heart catheterisation shows prominent v waves in the wedge tracing and no oxygen saturation step up.
• Coronary angiography to define culprit and disease for concurrent bypass.
• Chest radiograph for pulmonary oedema (often asymmetric if jet directed to the right upper lobe vein).

Stabilisation (bridge to surgery)

• Afterload reduction: sodium nitroprusside 0.25 to 0.5 micrograms/kg/min if blood pressure above 100 mmHg.
• Intra aortic balloon pump.
• Inotropes (dobutamine) and diuretics (furosemide 40 to 80 mg IV) as needed.
• Intubation and mechanical ventilation with PEEP; avoid hypovolaemia. VA ECMO or Impella (in selected cases) for refractory shock.

Definitive therapy

• Urgent surgery irrespective of stability. Mitral valve replacement is most common, because necrotic tissue limits repair; preservation of subvalvular apparatus where possible. Repair is sometimes feasible (papillary muscle reimplantation, chordal techniques).
• Coronary revascularisation at the same time when indicated.
• Transcatheter edge to edge repair has been used in nonoperative candidates.
• Early postoperative survival of 70 to 80% in experienced centres, with 5 year survival around 50 to 60%.

Postoperative

Anticoagulation (warfarin INR 2.5 to 3.5 for mechanical valve; 3 months for bioprosthesis), heart failure therapy and secondary prevention.